It seems an earlier run of the management command to fix Mach Billables was in error

One of the runs set the billable_date to today (today being early november ish) instead of the date of the message log, and this affected billables dating back to august. As a result november had a lot of augusts' billables due to this misrun.

I also made sure that only one billable per message log id was ever counted toward a bill.